The invention relates to an index apparatus for an NC machine tool.
An index apparatus for an NC machine tool is disclosed in U.S. Pat. Nos. 4,884,474 and 4,991,463 to the inventor of the application. The NC machine tool includes a spindle, a main table and an NC device for making a machining relative movement between the spindle and the main table. The apparatus includes a housing mounted on the main table. The apparatus further includes an index table on which a work is held, the index table being supported on the housing for rotation. The apparatus is a push bar type which includes a single push bar extending into the housing and outwardly of the housing for longitudinal movement, the NC device being arranged to make an extra relative movement between the spindle and the main table other than the working relative movement, so that the single push bar can be pushed and moved longitudinally thereof by the extra relative movement between the spindle and the main table to rotate the index table in one direction when indexing the work.
The apparatus is advantageous in that it can index the work in accordance with the programming of the NC device, obtaining a high productivity. Unlike an electric, hydraulic or pneumatic type of index apparatus, the apparatus does not involve an electric, hydraulic or pneumatic drive means for rotating the index table, to be simple in structure and low in cost. It is not required to make an electric wiring, hydraulic piping or pneumatic piping on the main table. Accessories such as pallet changer can therefore installed at will without problem of space. As a result, the apparatus has been winning a high recognition up to the present on the market of NC machine tool.
However, the apparatus is questionable in that it can merely rotate the index table in one direction. The apparatus can not rotate the index table in the reverse direction to index the work, obstructing the operating efficiency. It is therefore desired to rotate the index table not only in one direction but also in the reverse direction to index the work, improving the operating efficiency.
It is therefore an object of the invention to provide a new push bar type of index apparatus which can rotate an index table not only in one direction but also in the reverse direction, to overcome the above problem.
According to the invention, there is provided an index apparatus for an NC machine tool, the NC machine tool including a spindle, a main table and an NC device for making a machining relative movement between the spindle and the main table.
The apparatus comprises a housing mounted on the main table. An index table is supported on the housing for rotation. The apparatus further comprises first and second push bars extending into the housing and outwardly of the housing for longitudinal movement, the NC device being arranged to make an extra relative movement between the spindle and the main table other than the machining relative movement, so that any one of the first and second push bars can be pushed and moved longitudinally thereof by the extra relative movement between the spindle and the main table. The apparatus further comprises transmission means received in the housing and disposed between the first and second push bars and the index table to rotate the index table in one direction in response to the longitudinal movement of the first push bar and in the reverse direction in response to the longitudinal movement of the second push bar.
In a preferred embodiment, the NC machine tool comprises a machining center in which a work is held on the index table, a tool being held on the spindle. The NC device makes the machining relative movement between the spindle and the main table so that the work can be machined by the tool.
A work may be held not on the index table but on the spindle to be machined by a tool which is held on the index table.
The NC machine tool may comprise an electric discharge machine in which a work is held on the index table, electrically discharging means being held on the spindle. The NC device makes the machining relative movement between the spindle and the main table so that the work can be machined by the electrically discharging means.
The first and second push bars are fitted into first and second sleeves to extend parallel to each other for longitudinal movement. The first and second sleeves are disposed and fixed in the housing.
The apparatus further comprises spring means for resiliently urging the first and second push bars so that the first and second push bars can be returned by the spring means after the longitudinal movement, for reciprocating movement. The transmission means rotates the index table at an angle for one reciprocating movement of the first or second push bar.
The index table includes a shaft extending into the housing, the first and second push bars being disposed on the opposite sides of the shaft. The transmission means comprises first and second pawls extending inversely to each other and mounted on the first and second push bars. The transmission means further comprises a ratchet wheel including teeth and mounted on the shaft. The first or second pawl is engaged with one of the teeth of the ratchet wheel to rotate the ratchet wheel and index table in response to the longitudinal movement of the first or second push bar.
The apparatus further comprises a locking member for locking the index table from rotation. The apparatus further comprises unlocking means by which the locking member is moved to unlock the index table for rotation in accordance with the longitudinal movement of the first push bar when moved longitudinally thereof to a predetermined position. An auxiliary member is disposed between the first and second push bars so that the first push bar can be moved longitudinally thereof to the predetermined position by the auxiliary member in accordance with the longitudinal movement of the second push bar.